Aortic aneurysms represent a significant medical problem for the general population. Aneurysms within the aorta presently affect between two and seven percent of the general population and the rate of incidence appears to be increasing. This form of vascular disease is characterized by a degradation in the arterial wall in which the wall weakens and balloons outward by thinning. If untreated, the aneurysm can rupture resulting in death within a short time.
The traditional treatment for patients with an abdominal aortic aneurysm is surgical repair. This is an extensive operation involving transperitoneal or retroperitoneal dissection of the aorta and replacement of the aneurysm with an artificial artery known as a prosthetic graft. This procedure requires exposure of the aorta through an abdominal incision extending from the lower border from the breast bone down to the pubic bone. The aorta is clamped both above and below the aneurysm so that the aneurysm can be opened and the prosthetic graft of approximately the same size as the aorta can be sutured in place. Blood flow is then re-established through the prosthetic graft. The operation requires a general anesthesia with a breathing tube, extensive intensive care unit monitoring in the immediate post-operative period along with blood transfusions and stomach and bladder tubes. All of this imposes stress on the cardiovascular system. This is a high-risk surgical procedure with well-recognized morbidity and mortality.
More recently, significantly less invasive clinical approaches to aneurysm repair known as endovascular grafting have been proposed. (See, Parodi, J. C., et al. "Transfemoral Intraluminal Graft Implantation for Abdominal Aortic Aneurysms," 5 Annals of Vascular Surgery, 491 (1991)). Endovascular grafting involves the transluminal placement of a prosthetic arterial graft in the endoluminal position (within the lumen of the artery). By this method, the graft is attached to the internal surface of an arterial wall by means of attachment devices such as expandable stents, one above the aneurysm and a second below the aneurysm.
It is not uncommon for abdominal aortic aneurysms to extend to the aortic bifurcation or even into the common iliac arteries. When the aneurysm extends into the common iliac arteries it is necessary that the graft system used to repair the aneurysm extend into the common iliac arteries past the aneurysm. This requires that there be enough space between the aneurysm and the common iliac bifurcation so that the graft can properly seat. By "seating" it is meant that the graft is somehow fixed to the non-aneurysmal vasculature. However, in a significant number of patients the aneurysm extends into the common iliac arteries on one or both sides such that there is not enough room to seat the graft without at least partially blocking the internal iliac artery. Such a situation occurs in so-called Class D or E aneurysms. The internal iliac artery is a significant vessel which supplies blood to the pelvic region. Blockage of the vessel can result in undesirable consequences for the patient. For this reason, patients in this category are often excluded from the less expensive and less traumatic endovascular repair and must instead undergo the invasive surgical procedure described above.
Therefore, a need exists for an improved prosthetic graft which will allow endoluminal reconstruction of the common, external, and internal iliac bifurcation. The preferred construction will allow a bifurcated or biluminal aortic graft system to be implanted prior to or following the reconstruction of the iliac bifurcation, while maintaining blood flow to the internal iliac arteries.